Kidneys: anatomy, role, size, pain, diseases, exams

The kidneys are part of theUrinary System. Homeostasis, hormonal functions, regulation of blood pressure, filtration and elimination of waste… Although it is possible to live normally following the removal of a kidney, these organs provide essential body functions. “In the kidneys, the glomeruli are the units of blood filtration. They produce primitive urine. By a work of reabsorption, the primitive urine is remodeled in tubules whose main function is to reabsorb a large part of the water, calcium, potassium and sodium it contains. A system that allows the recovery of all the elements that the organism needs and the elimination of what is not necessary for the organism”. explains Nicolas Maillard, nephrologist at the Saint-Etienne University Hospital.

The kidneys are two organs located in the posterior part of the abdomen at the level of the lumbar regions, on either side of the spine. Elements of the urinary system, the kidneys are connected to the bladder by two large channels, the ureters. On average, according to the National Cancer Institute, a kidney is about 12 centimeters in height, 6 centimeters wide and 3 centimeters thick. It is composed of tubules, vessels and glomeruli. “The kidneys have a microscopic architecture, the essential is not visible to the naked eye. There are very small structures, the glomeruli, which play a major role in the filtration of waste. These glomeruli are small units of filtration, numbering about a million in each kidney”, says Nicolas Maillard.

⇒ Filtration role : “The first function of the kidney is the function of purifying the blood of what are called uremic toxins, i.e. all the molecules which would accumulate in the blood in the absence of the kidneys. There are more than 500 known molecules, as many who are not”says our expert. “The kidneys also provide detoxification functionthis time under the action of tubular cells.”

⇒ Thehomeostasis : “It’s about maintaining the necessary amount of water, sodium, potassium or even chlorine in the body.” The kidneys manage the management of these balances and ensure the output of several elements of the body including:

• Water: the kidneys eliminate excess water; renal function-specific elimination.
• Sodium, potassium: in case of renal insufficiency, their accumulation can also make uremic toxins.

⇒ Endocrine functions. The kidneys contribute in particular to the production of red blood cells thanks to the secretion of erythropoietin which stimulates the bone marrow and leads to the production of hemoglobin and red blood cells. They transform vitamin D, obtained in food or by exposure of the skin to the sun, into so-called active vitamin D, also called calciferol, which allows the absorption of calcium and phosphorus at the intestinal level. The kidneys secrete renin, a hormone that helps regulate blood pressure.

⇒ Management of acid-base balance : “It is a balance between the acidity and the alkalinity of the body which allows a close control of the pH and which ensures the proper functioning of cells and blood particularly.”

Kidney symptoms and problems will depend on how much kidney function remains. “In most cases it is progressive diseases which lead to chronic renal failure at various levels”comments the nephrologist.

The most common causes of chronic kidney disease:

• The diabetic glomerulosclerosis : Diabetes causes frequent damage to the glomeruli, the most frequent cause of chronic renal failure.
• The inflammatory glomerular diseases like Berger’s disease
• Some drugs are called nephrotoxic. In this case, it is an attack of the tubules.
• The urological diseases: calculations, malformations of the urinary tract can lead to chronic renal failure, of urological origin. This is again an attack of the tubules.
• The genetic diseases such as polycystic kidney disease, the most common genetic disease that results in numerous cysts in both kidneys. The kidneys become very large and very heavy, causing chronic renal failure.
• From pyelonephritis Repeated kidney infections with bacteria can cause chronic kidney failure.

Possible consequences of chronic kidney disease

• Increased cardiovascular risk due to high blood pressure caused by the accumulation of water and sodium in the blood.
• Increased cardiovascular risk (stroke, heart attack) due this time to the accumulation of uremic toxins, causing calcification of the arteries and development of atherosclerotic plaques
• Arterial hypertension reaches the vessels of the kidneys which are then no longer sufficiently supplied with blood.
• Increased potassium with risk of cardiac arrest.
• Erythropoietin secretion deficiency leading to anemia and a drop in hemoglobin levels.
• Deficiency of active vitamin D which leads to bone disorders like renal osteodystrophy.

Diagnosis of renal failure is made by blood creatinine level. “It is a small molecule, a biomarker produced by the muscles, eliminated only by the kidneys. The higher the level in the blood, according to a calculation which takes into account several factors, the more it indicates a reduced functioning of the kidneys. .” This calculation estimates the glomerular filtration rate, expressed in ml/min/1.73 m2, i.e. the volume of fluid filtered by the kidneys every minute. “Below 60, it is considered that he suffers from chronic renal failure”, explains Nicolas Maillard. “It exists five stages of chronic kidney diseasestage 5 being called “terminal” But that doesn’t mean we’re going to die!”, reassures the specialist. Indeed, the so-called techniques of renal replacement which are the techniques of dialysis and renal transplantation make it possible to live despite an advanced stage of chronic renal insufficiency.

Thanks to Dr. Nicolas Maillard.

On the health forum: discussions about the kidneys

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